What is Ligo: Definition and 97 Discussions

The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory designed to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. Two large observatories were built in the United States with the aim of detecting gravitational waves by laser interferometry. These observatories use mirrors spaced four kilometers apart which are capable of detecting a change of less than one ten-thousandth the charge diameter of a proton.The initial LIGO observatories were funded by the National Science Foundation (NSF) and were conceived, built and are operated by Caltech and MIT. They collected data from 2002 to 2010 but no gravitational waves were detected.
The Advanced LIGO Project to enhance the original LIGO detectors began in 2008 and continues to be supported by the NSF, with important contributions from the United Kingdom's Science and Technology Facilities Council, the Max Planck Society of Germany, and the Australian Research Council. The improved detectors began operation in 2015. The detection of gravitational waves was reported in 2016 by the LIGO Scientific Collaboration (LSC) and the Virgo Collaboration with the international participation of scientists from several universities and research institutions. Scientists involved in the project and the analysis of the data for gravitational-wave astronomy are organized by the LSC, which includes more than 1000 scientists worldwide, as well as 440,000 active Einstein@Home users as of December 2016.LIGO is the largest and most ambitious project ever funded by the NSF.
In 2017, the Nobel Prize in Physics was awarded to Rainer Weiss, Kip Thorne and Barry C. Barish "for decisive contributions to the LIGO detector and the observation of gravitational waves".Observations are made in "runs". As of December 2019, LIGO has made 3 runs, and made 50 detections of gravitational waves. Maintenance and upgrades of the detectors are made between runs. The first run, O1, which ran from 12 September 2015 to 19 January 2016, made the first 3 detections, all black hole mergers. The second run, O2, which ran from 30 November 2016 to 25 August 2017, made 8 detections, 7 black hole mergers, and the first neutron star merger. The third run, O3, began on 1 April 2019; it is divided (so far) into O3a, from 1 April to 30 September 2019, and O3b, from 1 November 2019 until it was suspended in March 2020 due to COVID-19.

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  1. Bmaxwell

    Exploring Black Holes: Uncovering Inner Structures with Gravity Waves

    I'm a structural engineer in Mississippi and I love all aspects of cosmology. I want to learn all I can about gravity wave technology. I was not expecting the level of detail that a single event is revealing. It's very interesting that they expect to see gravity waves from objects other than...
  2. M

    What's New in Gravitational Fields and Waves? A Welcome Back to PF!

    Hi, previously at Cardiff Uni, now at Buckingham, I'm still interested in gravitational fields, waves, Einstein, LIGO and all that.
  3. I

    Programs Has anyone heard back from Caltech for the LIGO summer program?

    Hi everyone, I have applied to the LIGO summer program. But I'm not from Caltech. I'm wondering if anyone has heard back from Caltech yet. Thanks
  4. Y

    B Dose LIGO verify GR definitely?

    LIGO announced the detection of gravitational wave event GW150914, which coincided with the numerical waveform predicted by GR. The PRL paper says "Using fitting formulas calibrated to numerical relativity simulations, we verified that the remnant mass and spin deduced from the early stage of...
  5. H

    B Exploring Ligo: Uncovering the Mystery Behind the Famous 'Chirp' Pulse

    Is another subforum for Ligo, I see nothing in here(? My main question is on all the popular media reports i have only seen the one pulse, the now famous chirp If the thing works why isn't it swamped with signals??
  6. Jonathan Scott

    A Gamma ray burst associated with LIGO GW event

    Quite unexpectedly, it seems that the Fermi Gamma-ray Burst Monitor spotted what appears to be a hard gamma-ray burst about 0.4s after the LIGO GW event, lasting about 1s: http://arxiv.org/abs/1602.03920 This is not expected from a black hole merger (and as a black hole sceptic, I find it very...
  7. JK423

    How did LIGO estimate the distance of the black holes?

    As we all know, the LIGO collaboration published a paper recently on the first direct observation of a binary merging black hole system. From the observed signal, they were able to infer the black holes' masses and their distance from Earth. However, the fact that they can estimate masses and...
  8. Cuboctonion

    Q&A: LIGO Gravitational Wave Detection

    I have a couple of questions regarding the new detection of signals believed to be gravitational waves at LIGO 1. Two similar signals were detected at both facilities. Why does the Livingston signal appear to be weaker than the Hanford signal? 2. The signal in Livingston was reported to have...
  9. Jorrie

    How is the redshift of gravitational wave events measured?

    LIGO reported the announced event with a redshift of 0.6 < z < 1.3. With no em radiation event reported (AFAIK), does anyone know how they have determined the redshift? I understand how they could measure the pre-merger, chirp and ring-down frequencies with good accuracy. In order to determine...
  10. G

    GW Detection Confirmation: Time, Rate, & GRB?

    I understand that the LIGO experiment was very lucky to find a very strong signal of a very energetic event (binary black hole merger). Having into account the non-negligible possibility that the signal may be spurious or some problem in the data adquisition, how much time must pass before we...
  11. G

    Many questions about the LIGO Gravity Wave Experiment....

    I'd like to understand the details behind the LIGO experiment a bit better: How do scientists know that the gravitational waves detected by LIGO originated from two specific black holes (located a billion light years away)?Does the LIGO result confirm the existence of black holes?Was it only...
  12. M

    I LIGO Discovery - A question about space-time properties

    A question from a physics laymen to those more advanced: if eLIGO detects gravitational waves by the difference to the combined laser wavelengths (a difference to the destructive interference pattern following curvature of space-time in each individual pathway), how is it that the lasers...
  13. C

    What is the Source of 3 Sun M Energy Released in BH Merger?

    Each of the two BHs in the collision brought in matter and energy prior to merge, neither emitting any significant energy prior to merge. Same for the combined BH after merger was complete. So, my question is, what is the source or mechanism for the 3 Sun M worth of energy release into...
  14. anorlunda

    Damping of Gravitational Waves

    Like many others, LIGO made me curious about gravitational waves. I found the paper: Nonlocal Gravity: Damping of Linearized Gravitational Waves http://arxiv.org/abs/1304.1769 I'm having difficulty understanding. Does that mean that damping is implicit in the terms of the tensors? Does it...
  15. pixel

    Detecting Interference Pattern Changes in LIGO Measurement

    As the length distortion due to a gravitational wave as it passes by Earth is on the order of the dimension of an atom, or << a wavelength of light, can someone describe in a general sort of way what measurement steps are employed to detect such small changes in an interference pattern? It would...
  16. bcrowell

    What is the significance of the recent LIGO result and its impact on textbooks?

    The recent LIGO result seems likely to lead to a lot of rewriting of textbooks. Some topics that occur to me: (1) Obviously it needs to be discussed in any GR textbook's discussion of gravitational waves. (2) The fact that the waveform matches so well with GR calculations seems to be extremely...
  17. D

    Hasn't Gravitational Lensing Already Proved Einstein? (LIGO)

    The news out of LIGO is being heralded as one of the most important experimental verifications of physics in decades, as it provides experimental support to the General Theory. The news makes it seem as though it were like the Higgs Boson was; theoretically concrete, but up in the air until...
  18. R

    Questions About Spatial Orientation of Event w/ Respect to LIGO

    I didn't see these areas addressed, my apologies if I missed them. If there was no delay in the detection of the signals at the two sites, would that mean that the location of the event was 'directly overhead' or 'directly below'? Was the delay, compared to the speed of light and distance...
  19. jim mcnamara

    Given the LIGO results lets use some humor

    http://xkcd.com/1642/ I've made a suggestion like this before. The LIGO results are wonderful, but the questions from "out there" sometimes display a level of understanding best dealt with the xkcd.com comic linked above. My opinion only. I've made this suggestion before. With regard to...
  20. F

    Can LIGO Data Replicate the Famous Michealson & Morley Experiment?

    Would it be possible to duplicate the Michealson & Morely experiment using LIGO data? Essentially the geometry seems to be the same , so I was wondering whether it would be possible verify the M&M result at a much higher resolution using existing LIGO data or is the stability not designed to...
  21. G

    Does LIGO Ruling Out Linear Gravity Theories?

    As the discovery matches templates based on GR, and the regime is of very strong gravitational fields and very high speeds (relativistic speeds), and there is a 90% match between model and measured data, this does rule out linear or quasi linear alternative theories of gravity?
  22. L

    Exploring the Roller Coaster Ride of LIGO Photons

    I am trying to understand how the photons in the LIGO beams behave when going along the "slopes" of the gravitational waves, in particular how the Shapiro delay gets factored into the resulting interference. To simplify the situation, suppose that a LIGO photon starts orthogonally to a wave...
  23. bcrowell

    I LIGO and speed of propagation of gravity

    Before the recent LIGO result, there was already not much doubt that gravitational effects propagated at c, but the evidence was indirect. To what extent does the LIGO result test this directly, and how will this be improved in the future? The H1 and L1 instruments are separated by 3002 km...
  24. phyzguy

    Rumors of 3rd LIGO Event: New Scientific Article Sheds Light

    I'm trying to reconcile yesterday's announcements with the rumors that have been reported. I and others have heard rumors of three events. Yesterday they reported on the event from 14-Sep-2015, and the paper LIGO-P1500217 titled "The Rate of Binary Black Hole Mergers Inferred from Advanced...
  25. S

    LIGO discovery on gravitational waves.

    Could someone please describe the recent LIGO project, gravitational waves and their detection in simple terms. PLEASE.
  26. bcrowell

    Dispersion of gravitational waves

    The LIGO paper https://dcc.ligo.org/LIGO-P150914/public puts limits on the dispersion of gravitational waves, which can be interpreted as an upper limit of 10^-22 eV on the mass of the graviton. We all know that low-amplitude gravitational waves are supposed to propagate at c according to the...
  27. websterling

    LIGO GW150914 Data Release & Tutorial

    https://losc.ligo.org/events/GW150914/']The[/PLAIN] LIGO Open Science Center has released data from the gravitational wave detection along with a tutorial going through some typical signal processing tasks on strain time-series data associated with it. GW150914 Data Release From the tutorial...
  28. ujjwal3097

    I LIGO [ meeting on Thursday on 11 feb 2016]

    Does anyone know where we can watch the live stream of the conference held at Washington DC on 11 feb 2016 10:00 am
  29. ohwilleke

    What do the gravity waves seen by LIGO imply for QG?

    LIGO will apparently announce on February 11, the detection at five plus sigma of gravity waves (3 solar masses of energy worth in about 100 seconds) emitted as two medium sized black holes of about 65 solar masses combined spiral into each other and merge into a single Kerr (i.e. spinning)...
  30. Math Amateur

    MHB Gravitational Waves Detected at LIGO?

    There are rumours that scientists at Advanced LIGO have detected gravitational waves ... it is about 100 years after Einstein predicted they were there in his mathematical theory of general relativity ... Anyone know more about this rumour ...? Peter
  31. phyzguy

    A Rumors of Gravitational Wave Inspiral at Advanced LIGO | Sept 2015 Launch

    There is a rumor going around that a gravitational wave inspiral has been seen at advanced LIGO. The web sites say it went on line in Sept, 2015, so I guess this is possible. Has anyone here heard anything?
  32. ShayanJ

    LIGO & GRB 070201 - Ruling Out a Neutron Star Merger

    Here, you can find the paragraph below: But I don't understand how a non-detection can mean the detection pf gravitational waves! Anyone knows what's the point? Thanks
  33. wolram

    Understanding LIGO and Its Implications

    From WIKI, In February 2007, GRB 070201, a short gamma-ray burst, arrived at Earth from the direction of the Andromeda Galaxy, a nearby galaxy. The prevailing explanation of most short gamma-ray bursts is the merger of a neutron star with either a neutron star or black hole. LIGO reported a...
  34. sophiecentaur

    Current Updates on LIGO and Gravitational Waves

    I had a quick Google and there was nothing very interesting with a recent date. It seems that the management introduced some 'test' data. a while ago, to see of the system worked and it was detected. I'm sure someone here must be a bit 'in the know' about what's going on.?
  35. B

    What Do the Purple Dots and Signs Represent in the LIGO Experiment Screensaver?

    Can anyone explain what the purples and signs are in this picture?
  36. P

    When will LIGO be sensitive enough to detect gravitational wave background?

    Advanced LIGO, scheduled to start in 2014, is believed to be able to detect gravitational waves from stellar sources. According to our best current models, does Advanced LIGO stand any chances of detecting the stochastic GW wave background? And even measure its temperature? (No more than 0.9K...
  37. C

    Caltech LIGO REU: Experiences & Reviews

    Hello, I was recently accepted into the LIGO REU at Caltech and was wondering if anyone here had any experience with the program? If so, could you provide a brief rundown of your summer experience? Thanks so much!
  38. K

    Gravitational Waves and the Role of Photons in LIGO

    This observatory is designed to detect gravitational waves, however, I feel that it won't work. I am sure I am wrong in my assumption, but I would like someone to explain to me why I am wrong. I feel that this machine will not work because the gravitational waves passing over the machine will...
  39. wolram

    Einstein@Home search for periodic gravitational waves in LIGO S4 data

    arXiv:0804.1747 [pdf, other] Title: The Einstein@Home search for periodic gravitational waves in LIGO S4 data Authors: LIGO Scientific Collaboration: B. Abbott, et al Comments: 29 pages, 19 figures Subjects: General Relativity and Quantum Cosmology (gr-qc) A search for periodic...
  40. S

    LIGO detects no gravitational waves from gamma ray burst

    On February 1, 2007, the Konus-Wind, Integral, Messenger, and Swift gamma-ray satellites measured a short but intense outburst of energetic gamma rays originating in the direction of M31, the Andromeda galaxy, located 2.5 million light-years away. The majority of such short (less than two...
  41. M

    Ligo: tHE eLEPHANT GETS wHITER?

    ok guys maybe I missed something but this project looks more and more like a Hi Fi enthusiast tuning his kit with excited enthusiasm. But no music is heard. :devil: Ok so a few years or so I said this would fail through an error of priciple. LOL I no nothing compared to these guys... so why...
  42. K

    Exploring Using LIGO as a Photon Buffer for Quantum Eraser Experiments

    Just a few questions for anyone. I am trying to buffer photons for a long delay quantum eraser. Is there anyway to convert one arm of a 4km LIGO interferometer into a high-fidelity photon buffer? If a beam is merely reflected once down the length of the tube, it is stored for ~13 µs with...
  43. marcus

    Gravity waves not seen on 2nd try (LIGO)

    Posted 6 May 2005 http://arxiv.org/abs/gr-qc/0505029 Upper limits on gravitational wave bursts in LIGO's second science run Authors: LIGO Scientific Collaboration 23 pages, 14 figures, to be submitted to Phys Rev D "We perform a search for gravitational wave bursts using data from...
  44. K

    LIGO and speed of gravitational waves

    LIGO may have failed to detect gravity waves because they move faster than light and so have a greater wavelength than expected and probably a lower amplitude too.
  45. K

    LIGO and speed of gravitational waves

    LIGO may have failed to detect gravity waves because they move faster than light and so have a greater wavelength than expected and probably a lower amplitude too.
  46. K

    Gravity & LIGO: Wave Length, Amplitude & Gravitons

    What is the wavelength and amplitude of the gravitational waves that LIGO is trying to detect? Are these waves made of gravitons (as light waves can be made of photons) and how much energy do they carry?
  47. A

    LISA and LIGO: Exploring Gravity Waves in Space & Earth

    Have you heard about the LISA project? It is an oversized version of LIGO (Laser Interferometer Gravitational Wave Observatory). LIGO is being built now, and it is basically two L shaped interferometers (one in Louisiana and one in Washington); each 4 km long. LISA will be a much bigger...
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